error_handler

Default System Error Handler

undefined_function(Module, Function, Args) -> any()

Module = Function = atom()

Args = list()

A (possibly empty) list of arguments Arg1,..,ArgN

This function is called by the run-time system if a call is made to
Module:Function(Arg1,.., ArgN) and
Module:Function/N is undefined. Note that
undefined_function/3 is evaluated inside the process
making the original call.

This function will first attempt to autoload
Module. If that is not possible,
an undef exception will be raised.

If it was possible to load Module
and the function Function/N is exported,
it will be called.

Otherwise, if the function '$handle_undefined_function'/2
is exported, it will be called as
'$handle_undefined_function'(Function,
Args).

Warning!

Defining '$handle_undefined_function'/2 in
ordinary application code is highly discouraged. It is very
easy to make subtle errors that can take a long time to
debug. Furthermore, none of the tools for static code
analysis (such as Dialyzer and Xref) supports the use of
'$handle_undefined_function'/2 and no such support
will be added. Only use this function after having carefully
considered other, less dangerous, solutions. One example of
potential legitimate use is creating stubs for other
sub-systems during testing and debugging.

Otherwise an undef exception will be raised.

raise_undef_exception(Module, Function, Args) -> no_return()

Module = Function = atom()

Args = list()

A (possibly empty) list of arguments Arg1,..,ArgN

Raise an undef exception with a stacktrace indicating
that Module:Function/N is
undefined.

undefined_lambda(Module, Fun, Args) -> term()

Module = atom()

Fun = function()

Args = list()

A (possibly empty) list of arguments Arg1,..,ArgN

This function is evaluated if a call is made to
Fun(Arg1,.., ArgN) when the module defining the fun is
not loaded. The function is evaluated inside the process
making the original call.

If Module is interpreted, the interpreter is invoked
and the return value of the interpreted
Fun(Arg1,.., ArgN) call is returned.

Otherwise, it returns, if possible, the value of
apply(Fun, Args) after an attempt has been made to
autoload Module. If this is not possible, the call
fails with exit reason undef.

Notes

The code in error_handler is complex and should not be
changed without fully understanding the interaction between
the error handler, the init process of the code server,
and the I/O mechanism of the code.

Changes in the code which may seem small can cause a deadlock
as unforeseen consequences may occur. The use of input is
dangerous in this type of code.